[Tutor] Handling 'None' (null) values when processing sqlite cursor results

[Andre Engels]

On Wed, Jul 14, 2010 at 6:31 AM, Monte Milanuk <memilanuk at gmail.com> wrote:
> Hello all,
>
> I'm struggling a bit trying to find the right way to deal with null values
> in my sqlite database when querying it and processing the results in python.
>
> If my cursor.fetchall() results return the following:
>
> (104, None, u'Sylvester', None, u'Evans', None, u'527-9210 Proin Av.',
> u'Liberal', u'VT', u'24742', u'1-135-197-1139',
> u'vehicula.Pellentesque at idmollis.edu', u'2010-07-13 22:52:50', u'2010-07-13
> 22:52:50')
>
> At first I was having fits as str.join() was giving me a 'NoneType error'.
>  I found one way around that, by processing the results so the 'None' values
> got omitted from the list by the time they got to str.join().
>
> I thought that was the end of that, until I tried working with the returned
> records in another fashion and found that having the 'None' values omitted
> really messed with the list order which I was depending on i.e. list[5]
> could be different fields depending on how many 'None' values had been
> omitted.  And if I didn't omit them, when I printed out the user name in the
> format 'first''middle''last' from the above record, I got
> 'Sylvester''None''Evans' rather than just 'Sylvester''Evans' (i.e. with no
> middle initial).
>
> So... I guess my question is, is there a good/proper way to handle the
> 'None' values as returned by sqlite from a table that may have some null
> values in individual records?  Basically I want not have the None/Null
> values show up but to keep them as place holders to make sure i get the
> values in the right spots...

It depends a bit on what you want to do with the values. My preference
would be to keep the result of cursor.fetchall(), and instead
re-define the output function(s) that I use (so don't use
str.join(record), but some myjoin(str,record) that I defined). Or,
even better, to define a class for these, create an object of the
class from the fetchall result, and have things like the myjoin before
as class methods or properties.

-- 
André Engels, andreengels at gmail.com